The study of novel two-dimensional structures for potential applications in photocatalysis or in optoelectronics is a challenging task. In this work, first-principles calculations have been carried out to explore the properties of the two-dimensional perovskite-based MgPSe3. Dynamic and mechanical analyses confirm the stability of this low-dimensional material. Our calculated Raman frequencies are in good agreement with previous studies. Furthermore, a topological bonding analysis, based on the electron localization function, indicates a covalent and ionic character for the P-Se and Mg-Se bonds, respectively. From a reactivity point of view, water interacts poorly with MgPSe3 and its associative interaction is physisorbed and governed by weak interactions. Consequently, the low dissociative energy of H2O molecules affects the reaction taking place on the surface of the material, making it unfavorable for both hydrogen and oxygen evolution reactions. However, the computed electronic properties show that MgPSe3 is a promising material for optoelectronic applications.